Cardiopulmonary resuscitation (CPR) is a procedure performed as life-saving first aid in the case of a sudden cardiac arrest. The procedure comprises chest compressions and ventilation. Recent publications have pointed out numerous problems with how CPR is being conducted today by professionals.
Aufderheide et al showed in their publication “Hyperventilation-Induced Hypotension During Cardiopulmonary Resuscitation”, Circulation. 2004;109 that trained Emergency Medical Services (EMS) personnel had problems ventilating correctly. Even after re-training, the ventilation rate was still too high compared to the “Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care” published by The American Heart Association, in collaboration with International Liaison Committee on Resuscitation, herein after referred to as “the Guidelines”.
Van Alem, Sanou and Koster pointed to another problem with the performance of CPR in “Interruption of Cardiopulmonary Resuscitation With the Use of the Automated External Defibrillator in Out-of-Hospital Cardiac Arrest”, Annals of emergency medicine 42:4 (October 2003); even trained EMS personnel that performed CPR conducted compressions or ventilations less than 50% of the time at the scene, i.e. hands-off time/inactivity time was too high.
Two articles in the Journal of the American Medical Association (JAMA) published Jan. 19, 2005, Vol 293, No. 3, “Quality of Cardiopulmonary Resuscitation During In-Hospital Cardiac Arrest” by Abella et. al. and “Quality of Cardiopulmonary Resuscitation During Out-of-Hospital Cardiac Arrest” by Wik et. al., conclude that hands off time was too high, the correct compression depth not reached, compression rate was either too low or too high and that hyperventilation happened frequently.
A CPR device is described by Halperin et al in U.S. Pat. No. 6,390,996, “CPR Check Compression Monitor”. This device only considers compression. The device uses an accelerometer and a gyroscope and measures continuously. This means that in the case of the rescuer not relieving pressure on the patient's chest between compressions, an error in the measurements will gradually build up.
Other, simpler CPR assist devices base their feedback on force and time. One such device is CPREzy from Medteq Innovations Pty. Ltd.
Some CPR assist devices are part of an Automatic External Defibrilator (AED) or a manual defibrilator. However, acquiring a new defibrillator with a CPR assist device might not be an option for Emergency Medical Systems (EMS) which already have a well functioning AED/Defibrilator system. Such EMS systems would rather consider a standalone solution for CPR measurement and feedback.
One combined CPR assist device and AED device is the CPR-D•padZ™ which is a part of the AEDPlus from Zoll Medical Corporation. This device only considers compressions, and provides audio feedback such as voice instructions and a metronome and visual feedback in the form of numbers on the AED screen.
None of these systems or devices provide feedback on both compression and ventilation activity and they neither provide feedback on inactivity or incomplete hand release/leaning through the full procedure of CPR. These issues are believed to be very important in increasing CPR performance and thus survival rates.
Another problem related to known systems, such as for example the AEDplus from Zoll, is that they are relatively expensive, big and complicated; so that lay rescuers are not likely to keep them available at all times.
Devices made for lay rescuers are described in EP1578340 (Laerdal Medical AS), which describes force sensitive devices giving sound signals for assisting the rescuer, and more particularly a device for placement between the hands of a person performing chest compression and the chest of a patient. Even more particularly the device being the subject of EP1578340 is designed to emit a sound when chest compression is performed with a force exceeding a pre-defined value and optionally also to emit a sound indicating the desirable rate of chest compression. This is obtained in an inexpensive and compact device which may be battery independent and thus always ready for use, or in an embodiment using a battery having very low power consumption.
Practice has shown that sound signals in some cases may be difficult to hear, especially in some emergency situations. The feedback of prior art feedback devices can also often interfere with other events and other information given at the rescue scene and the rescuer can often feel that the feedback is offensive and disturbing in a stressed situation.
Also, there is in some instances a need for a more accurate basis for the feedback to the user. If, for example, the applied force is too strong, there is a risk of hurting the patient. Thus there is in such instances a need for an energy efficient and compact device for providing quality CPR feedback, where the feedback is provided in a way which is dependable and likely for the rescuer to receive and perceive under all possible situations.